We report on a 45-year-old patient who sustained an intra-operative pulmonary thromboembolism during elective mastoidectomy under general anesthesia. At the end of surgery, the patient developed hemodynamic compromise and exhibited T wave inversion on electrocardiogram. Echocardiography showed an echogenic mass in the right pulmonary artery and pulmonary hypertension. Pulmonary thromboembolism is rare in the field of otolaryngology and head and neck surgery; however, it may develop, resulting in a fatal outcome. It is thus important to establish the diagnosis early and prevent such serious complications.